Ultrasound (US) imaging has provided useful information about the interior characteristics of an object or subject under examination. A US imaging system has included an ultrasound probe housing a transducer array that is configured to transmit an ultrasound signal into a scan field of view and receive echoes produced in response to the ultrasound signal interacting with structure of an object or subject therein. As the ultrasound signal traverses the object or subject, portions of the ultrasound signal are attenuated, scattered, and/or reflected off structure and/or boundaries in the interior of the object or subject, with some of the reflections traversing back towards the transducer array. The later reflections (or echoes) are received at the transducer array. In B-mode imaging, the echoes correspond to an axial slice through the object or subject and are processed to generate scanlines, which are used to produce a scanplane, or a two or a three dimensional image of the slice or volume, which are displayed via a display monitor.
Laparoscopic ultrasound examinations have been used to detect tumors in cavities. Generally, there are two types of ultrasound imaging probes—flexible and rigid. Flexible ultrasound probes include an articulating portion that can be controllably articulated to move an end of the probe with a transducer array through an angle of up to ninety (90) degrees in one to four planes. FIGS. 1A and 1B show an example of a flexible probe 100; namely, a laparoscopic transducer type 8666, which is a product of BK-Medical ApS, a company of Herlev, Denmark, which is a wholly owned subsidiary of Analogic Corporation, a company of MA, USA. As shown in FIG. 1A, the probe 100 is configured to articulate between a zero position 102 and an up position 104 and a down position 106. As shown in FIG. 1B, the probe 100 is configured to articulate between the zero position 102 and a left position 108 and a right position 110. In contrast, rigid probes are not configured to articulate as such and remain at the zero position 102. A lab probe can also be rigid in one direction, or only have motion in one plane. Furthermore this can be combined with a rotational motion of the array (i.e., can be combined with all the above).
An indicator used to guide biopsies has been the stiffness of the tissue, as unhealthy tissue is often stiffer than surrounding healthy tissue. Tissue stiffness has been determined with ultrasound using a technique referred to as elasticity imaging. With elasticity imaging, a mechanical compression (e.g., via vibration) is applied to tissue, with the unhealthy tissue compressing less than the surrounding tissue since the strain is less than the surrounding tissue. The mechanical compression has been applied by having the user of the probe push the probe against tissue of interest in a fluctuating manner to compress (e.g., 1 mm or so) and decompress the tissue. The measured stiffness has been overplayed on top of the B-mode image. With laparoscopic imaging, there is no direct visibility of the probe and the tissue, except when used with a camera, thus making it difficult to apply suitable manual compression to the tissue. Furthermore, since flexible probes by nature can be twisted and rotated, it may be difficult to manually apply the requisite force in the right direction and in a stable recurrent manner. Moreover, the length of the transducer may make it difficult to manually apply the oscillating pressure at the tip of the probe.